<p>Shelf-life extension of perishable foods is vital for ensuring food security and reducing postharvest waste. Tomato fruits are highly perishable due to microbial spoilage and physiological deterioration. This study evaluated the effectiveness of mango seed starch, lemon essential oil, lemon peel powder, and aqueous extracts of lemon peel and pomace in prolonging the shelf life of tomatoes. Treated tomatoes were monitored over an 11-day storage period, alongside an untreated control, for key quality parameters including colour index, firmness, weight loss, disease incidence, and disease severity. Results showed that lemon essential oil (LEO) significantly delayed ripening, maintaining a lower average colour index (2.02) compared to the control (2.46), and also preserved firmness (mean firmness index: 2.78 vs. 2.09 in control). LEO also reduced weight loss by 19.3% at the end of the storage period (36.7% vs. 45.5% in control). Lemon pomace extract (LPOE) had the lowest average weight loss (12.93%), while lemon pomace powder maintained the highest shelf-life score (mean 2.26 vs. 2.09 in control). All treatments significantly reduced disease severity and incidence compared to the untreated fruits. For instance, LEO and LPOE completely inhibited disease incidence for the first 3–4 days, whereas the control reached 60% incidence by day 2. Gas Chromatography–Mass Spectrophotometric (GC–MS) analysis revealed the presence of various bioactive compounds including n-Hexadecanoic acid (up to 15.27%) and 9,12-Octadecadienoic acid (7.26%), known for their antimicrobial and antioxidant properties. The findings suggest that agro-waste-derived treatments, particularly lemon oil and pomace extract, offer sustainable and eco-friendly alternatives to synthetic chemicals for postharvest preservation and shelf-life enhancement of tomato fruits.</p>